1) Field of the Invention
The invention relates to a tank cap with a cap part and with a filler neck for a refueling nozzle, wherein the filler neck can be closed by the cap part via a rotary closure, and with at least two seals arranged on the cap part and active between the cap part and the filler neck.
2) Description of the Related Art
In order to make tank caps for fuel tanks of motor vehicles liquidtight, it is common to arrange seals of various shapes and cross sections between the filler neck and the removable cap part. These seals are usually compressed by bayonet or thread means on rotation of the cap part and consequently bring about a type of seal to prevent liquid fuel from coming out. It is now known that, even if the seal makes good contact, fuel vapors can still escape to the outside as they diffuse through the seal. Recently, the level of fuel emissions caused in this way has to an increasing extent been drastically limited by statutory regulations. For fuel caps, the permitted permeation quantity is to be restricted to 3 milligrams of hydrocarbons per day (24 hours). Even with the most carefully designed seal, this cannot be achieved.
A tank cap which is designed in such a manner that this limit value can be observed is described in applicant""s Austrian Utility Model Application GM 610/99. In this case, a system comprising two seals is proposed for sealing the cap part in relation to the filler neck, one of which lies further in and the other further out relative to the filler neck. The seal lying further out includes an elastomer with high permeation resistance and is arranged in such a manner in relation to the seal lying further in that only a narrow gap remains between the two seals. This concept is highly suitable for more than meeting future legal requirements. However, the constructional embodiment described provides, in the inside of the filler neck, sealing surfaces for the seals which are exposed in such a manner that they can be touched and thus damaged by the refueling nozzle as it is inserted, which could impair the desired sealing function.
The object of the invention is to further optimize a tank cap of the type referred to in the introduction with a sealing system having at least two seals, and in particular, to ensure that damage cannot be caused to the sealing surfaces by the refueling nozzle.
According to the invention, the object is achieved by virtue of the fact that the sealing surfaces on the neck are in each case provided behind a raised region of a protuberance or the like and/or below at least one projection or the like.
According to a preferred embodiment of the invention, the seals are arranged on parts of the cap part which, for opening and closing, are held in a non-rotational manner in relation to the neck. The consequently smaller operating forces during opening and closing increase convenience. The seals are also subjected to less stress.
According to a further feature of the invention, the projection(s) and the protuberance are formed on the neck itself. A neck embodied thus can be manufactured easily by injection-molding.
According to a preferred embodiment of the invention, the projections are those parts of the anti-rotation arrangement provided on the neck, as a result of which the constructional complexity of the tank cap is reduced.
If the sealing surface is provided behind a raised edge region of a protuberance running around on the neck, it is designed in particular as a formation running around in a groove-like manner. A sealing surface embodied thus cannot be reached or touched by the filling pipe of a refueling nozzle.
In a tank cap embodied according to the invention, it is particularly important that the seals make as good contact as possible against the sealing surfaces on the neck. It is therefore advantageous if the seals can be pressed against these sealing surfaces in a spring-assisted manner.
The associated constructional embodiment can be effected in a simple manner in that the seal lying further in is arranged on a sealing part which is mounted vertically, counter to the force of at least one resilient element, on an element of the cap part, which element can be rotated for opening and closing.
According to the invention, the seal lying further out is arranged on an intermediate ring which is arranged between the sealing part and the element of the cap part which can be rotated for opening and closing, and is mounted rotatably in relation to the latter. A very expedient and functionally reliable arrangement of the seal lying further out is thus achieved.
In this connection, according to the invention, the at least one resilient element acts on the intermediate ring as well and thus, via the intermediate ring, presses the seal lying further out against its sealing surface on the neck. In this connection, the seal lying further out interacts with a conical support surface on the upper side of the sealing part. These configurations also bring about a very compact embodiment of the components involved.
The compact and very expedient construction continues in the configuration of the anti-rotation arrangement as well, projections or the like formed on the outer circumferential edge of the intermediate ring forming those parts of the anti-rotation arrangement interacting with the projections of the neck.